A. EMBODIMENT FOR MANDIBULAR RECONSTRUCTION
An alternate embodiment of the dental ramus implant shown in copending application Ser. No. 07/924,490 is treated in this disclosure. It is an alternative approach to the problem of mandibular reconstruction. It is a novel apparatus and method for restoring the mandible, lost through tumor resections, bone defects, pseudoarthosis or osteomyelitis.
The biomechanical advantages of the ramus clamp of U.S. Pat. No. 5,306,150 can be combined with means to restore the mandible to overcome several of the problems which face the Cranofacial or Maxillofacial Surgeon. The present design overcomes the following problems associated with conventional techniques:
a. Fastening to the boney stump posteriorly becomes more predictable in the unilateral situation;
b. Bilateral or entire jaw replacement is more easily accomplished with a secure and straightforward procedure; and
c. Dependency upon screws to anchor the posterior reconstruction is eliminated.
In the apparatus and method of the embodiment shown herein, no slots are made in the rami, but pre-designed clamps tightly grip the cortical surfaces and avoid the cancellous bone of the mandible, providing a secure hold without reducing the strength of the mandible.
B. EMBODIMENT FOR REPLACEMENT OF THE CONDYLAR PROCESS
In FIG. 2, a copy of FIG. 8 of Ser. No. 07/924,490 is shown as an alternate embodiment of the invention, for use in those situations in which the condyle or condylar process must be rebuilt or replaced. Portions of the condylar process 115, such as the head, neck, and pterygoid fovea may have deteriorated through disease or from accidental injury. A condylar process arm 120 may be fabricated as a substitute bearing surface for the defective natural condylar process.
As noted in U.S. Pat. No. 5,306,150, "it is also possible to apply this invention in the replacement of the condylar process and, of course, it may be applied in other defective condylar processes, elsewhere in the human anatomy, for which this construction is suitable."
The novelty of this invention resides primarily in the use of mechanically adjustable clamping apparatus and methods which do not weaken the cortical bone structure in order to securely mount a surgical clamp.
In the prior art, in the replacement of other defective condylar processes such as the condylar head of the femur, the prosthesis may be: forced into the femur; cemented in place; or screws may be driven into the bone.
The present invention avoids: crude pounding of the implant stem into the femoral canal, or equivalent canal in other bones, in order to achieve a press-fit of the implant; attempts to secure the shank of the implant within the internal bone canal with cements of uncertain reliability and indefinite life; and/or the use of wood screws, which rely upon the continuing elasticity of the bone to maintain solid contact between bone and prosthesis.
The present invention expands its clamps within the femoral canal in analogous fashion to the external clamping of the dental ramus clamp of U.S. Pat. No. 5,306,150. It uses a large bearing surface over which relatively low pressure can be maintained to secure and maintain solid bonding of prosthesis within the bone canal.
Other objects and advantages will become apparent in the following specification when considered in light of the drawings.